The present invention relates to a method of waste disposal.
Conventional methods of heating consist of fuel combustion and heat delivery to a material to be treated, by means of flame radiation and convection. Substantial disadvantages of the conventional methods are consumption of scarce kinds of fuel, nonuniformity of the temperature field and oxidizing atmosphere inside a furnace. Another conventional method is based upon the utilization of electrical energy. Disadvantages of these methods are a low overall energy efficiency and nonuniformity of the temperature field.
A fluidized bed reactor provides a means for coal combustion and for distribution of heat generation in the space of the reactor. However, this reactor can be used for heating only of fine, lumpy materials. Heat generated in the fluidized bed can be extracted only in a chamber separated from that of the combustion. The separation of the heat generation and extraction restricts application of such furnaces.
Uniform heating conditions and protective medium are acjieved by heating in a liquid bath. However, energy efficiency of these furnaces is low, and they use gaseous or oil fuel.
The most conventional way of gas heating consists in combustion. However, combustion changes the gas composition. in many cases, combustion is based on the utilization of scarse oil and gas fuel. Gas heating can also be carried out without changing the chemical composition by heat transfer between a heat source and a heated gas. Heat can be extracted from combustion products of high temperature wastes. Another conventional method of gas heating consists in a heat exchange between gases : one of these gases is a heat receiver, whereas the other of the gases is a heat source. Heat can be transferred through ceramic of metal walls separating the gas flows. This method is employed in boilers and recuperators. The drawback of such heating consists in the cost of material used for manufacturing gas exchangers and restrictions imposed on the temperature and pressure of a heated gas.
Another conventional method of gas heating consists in heat extraction from a heat source by a solid accumulator and heat transfer of this heat to a gas to be preheated. The implementation of this method by means of a periodical process is brough about in regenerators, caupers, stoves, and similar devices. Continuously this method is brought about in heat exchangers with moving elements (as disclosed for example, in R. Shchumann, 1952, p.p. 132-133). High thermal resistance of a solid restricts possible amount of heat accumulated. The temperature of gas heating is restricted and the cost of construction is relatively high.
The general shortcomings of conventional gas heating are their high cost, restricted temperature of preheating and impossibility to extract heat from all kinds of wastes, for example, from polluted gasses, from slag and so on.
Uniform heating conditions and utilization of chamical energy of carbon are achieved in steel-making converters and open hearth furnaces. However, the amount of heat available in these reactors is limited by the chamical energy of carbon disssolved in pig iron. this restricts application of this method.
The amount of energy available in a reactor similar to a converter can be increased by simultaneous injection of coal and air (oxygen) into a melt. One example of such reactors are given in the U.S. Pat. No. 3,711,275. However, the heat evolved in the reactors disclosed in this patent can be supplied pnly to a material absorbed in a bath. Sensible heat of flue gases and part of chemical energy of CO cannot be used in these reactors, and can be recovered only by means of air and material preheating. These drawbacks prevent effective utilization of the above mentioned method of material heating, and the described reactor cannot be used for gas heating.
One of the most promising sources of energy are different forms of the inductrial, agricultural and residential wastes. The inciniration of these wastes enables the utilization of their energy and at the same time the disposal of these wastes. Inciniration disposal in the final analysis is the only practical way of waste management. However, at present not all substances are completely destroyed in conventional inciniration sustems and there are condiderable siting difficulties, because of the known gaseous effluent and the adverse public opinion it creates. The present day incinirators to a great extent simply reproduce the design of conventional combusters, due to limited destruction experience and to operators familiarity with optimum fuel use. The requirements to a reactor for toxic waste disposal are, however, quite different from those applied to the today common usage of most efficient fuel combusters. Completeness of combustion and preparation of fuel have been optimized on present day incinirators for cost effectiveness and primization of overall operation, not destruction. The feasibility of the indiscriminate treatment of wastes as well as the total desctruction of toxic and offensive substances are on the contrary, the necessary condition for combustion of these species and not reactor operation for cost effective temperature and fuel use. The development of a system for indiscriminate waste inciniration with total destruction of hazardous and offensive substances is one of the conditions of the overall solution of waste problems.